TC easy way to play with spells for what suits your template.
Scribe is most powerful I've found if you have a buddy, two mystic scribe mages can lay down a nasty dump if you sync it right.
Focus for me was sufficient for PVP, never bothered with med on my mystic mage for pvp, but for PVM you'll absolutely want med.
If you're running out of mana, maybe you're using too many wasted spells.. The key to this temp as I mentioned is the dump.. Try to weaken em a bit, then if you can drop em down a few HP, or use mobs/pots to your advantage to knock em down a little, then you go big and dump.